Influence of Annealing and Composition on the Crystal Structure of Mixed-Halide, Ruddlesden-Popper Perovskites
Influence of Annealing and Composition on the Crystal Structure of Mixed-Halide, Ruddlesden-Popper Perovskites
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DOI：
10.1021/acs.chemmater.1c04213
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发表时间：
2022-04-12
影响因子：
8.6
通讯作者：
Stiff-Roberts, Adrienne D.
中科院分区：
文献类型：
--
作者：
Wright, Niara E.;Qin, Xixi;Stiff-Roberts, Adrienne D.
混合卤化物二维（2D）杂化有机-无机钙钛矿为控制光电器件中的应用的带隙提供了重要的机会。本研究的重点是苯乙基铵卤化铅[（PEA）（2）Pb（I1-xBrx）（4）]薄膜，其纯碘化物形式是研究最广泛的光学活性2D钙钛矿系统之一。共振红外，矩阵辅助脉冲激光蒸发用于生长薄膜，探讨生长后退火和混合卤化物成分的影响。研究了（PEA）（2）Pb（I1-xBrx）（4）（x = 0，0.25，0.5，0.75和1）薄膜的成分、晶体结构和光学性质。第一性原理计算与实验数据相结合，以解释混合卤化物的行为，不单调的趋势与溴化物含量。这项工作的重要结果如下：（i）X射线衍射揭示了卤化物在x = 0.25附近相分离的证据，与第一原理计算一致，而对于x = 0.5及以上没有观察到相分离，以及（ii）对于x = 0.75观察到独特的光致发光（PL）峰分裂，对于该组合物没有观察到组成相分离。PL分裂是暂时解释的两种不同类型的卤化物短程有序在x = 0.75的共存。总的来说，这项研究表明，混合卤化物n = 1 Ruddlesden-Popper钙钛矿不是简单的随机合金，而是它们显示不同的卤素阴离子的不同位点和排序偏好。这些偏好对于理解和合理调整材料的特性至关重要。
Mixed-halide two-dimensional (2D) hybrid organic-inorganic perovskites offer an important opportunity to control the band gap for applications in optoelectronic devices. This study focuses on phenethylammonium lead halide [(PEA)(2)Pb(I1-xBrx)(4)] films, the pure iodide form of which is one of the most widely studied optically active 2D perovskite systems. Resonant infrared, matrix-assisted pulsed laser evaporation is used to grow films to explore the effects of post-growth annealing and mixed-halide composition. The composition, crystal structure, and optical properties are studied for as-grown and annealed films of (PEA)(2)Pb(I1-xBrx)(4) for x = 0, 0.25, 0.5, 0.75, and 1. First-principles calculations are used in conjunction with the experimental data to explain the mixed-halide behavior that does not trend monotonically with the bromide content. Important results of this work are as follows: (i) X-ray diffraction reveals evidence for halide phase separation around x = 0.25, consistent with first-principles calculations, whereas no phase separation is observed for x = 0.5 and above and (ii) a unique photoluminescence (PL) peak splitting is observed for x = 0.75, a composition for which no compositional phase separation is observed. The PL splitting is tentatively explained by the coexistence of two distinct types of halide short-range ordering at x = 0.75. Overall, this study demonstrates that mixed-halide n = 1 Ruddlesden-Popper perovskites are not simple random alloys but that instead, they display distinct sites and ordering preferences of the different halide anions. These preferences are critical to understand and rationally tune the properties of the materials.